The Mediating Role of Social Participation in Motoric Cognitive Risk and its Relation to Depression and Loneliness in Older Adults.

BACKGROUND: Motoric cognitive risk syndrome (MCR) reduces the quality of life, independence, and social interaction in older adults. Social participation is a potentially modifiable factor that benefits cognitive and mental health. This study explored the mediating roles of social participation between MCR and depression and between MCR and loneliness. METHODS: We performed a secondary analysis of data from the 2015-2016 National Social Life, Health, and Aging Project. Slow gait speed and cognitive decline were used to assess MCR. Mediation analysis was applied to two models, both of which used MCR as an exposure and social participation as a mediator. The outcomes were depression and loneliness for each model, respectively. RESULTS: Among 1,697 older adults, 196 (11.6%) had MCR. The mediating role of social participation was statistically significant in both models. The indirect effect (ß=0.267, p=0.001) of MCR on depression through social participation comprised 11.97% of the total effect (ß=2.231, p<0.001). The indirect effect (ß=0.098, p=0.001) of MCR on loneliness through social participation was 19.48% of the total effect (ß=0.503, p<0.001). CONCLUSION: Interventions to increase social participation may reduce depression and loneliness of older adults with MCR.

Structural and Reactivity Effects of Secondary Metal Doping into Iron-Nitrogen-Carbon Catalysts for Oxygen Electroreduction.

While improved activity was recently reported for bimetallic iron-metal-nitrogen-carbon (FeMNC) catalysts for the oxygen reduction reaction (ORR) in acid medium, the nature of active sites and interactions between the two metals are poorly understood. Here, FeSnNC and FeCoNC catalysts were structurally and catalytically compared to their parent FeNC and SnNC catalysts. While CO cryo-chemisorption revealed a twice lower site density of M-Nx sites for FeSnNC and FeCoNC relative to FeNC and SnNC, the mass activity of both bimetallic catalysts is 50-100% higher than that of FeNC due to a larger turnover frequency in the bimetallic catalysts. Electron microscopy and X-ray absorption spectroscopy identified the coexistence of Fe-Nx and Sn-Nx or Co-Nx sites, while no evidence was found for binuclear Fe-M-Nx sites. 57Fe Mössbauer spectroscopy revealed that the bimetallic catalysts feature a higher D1/D2 ratio of the spectral signatures assigned to two distinct Fe-Nx sites, relative to the FeNC parent catalyst. Thus, the addition of the secondary metal favored the formation of D1 sites, associated with the higher turnover frequency.